The technical field of the invention is the control of hybrid vehicles, more particularly the control of hybrid vehicles having independent rear electric machines.
Hybrid vehicles with in-wheel motors comprise two traction systems and thus offer an additional option to that of all-electric vehicles.
The first traction system in such vehicles is purely electric. It comprises, on the rear axle set, two electric traction machines of the “in-wheel motor” type.
The second traction system is a heat engine propulsion unit made of up a combustion engine and a semiautomatic gearbox.
The vehicle is chiefly intended for electric use in town but also needs to be usable out of town.
Combustion engine operation gives the vehicle additional autonomy and a higher maximum speed as compared with the electric mode.
Electric operation is therefore deliberately limited to a maximum speed, for example of 90 km/h. An uncoupling system allows the electric machines to be disconnected above and beyond this speed. Thus the electric machines can be rated for a sufficient speed range, vehicle losses and therefore energy consumption beyond 90 km/h can be reduced and an additional safety barrier made available to ensure that the driver maintains control of the vehicle should the electric traction system malfunction.
Taking the design of this vehicle into consideration, it is absolutely essential to protect the traction electric machines from a risk of overspeed in operation. To do so, the speed of the electric machines under all nominal conditions of operation is limited, even when a wheel is skidding or no longer touching the ground. This then prevents a wheel from running away. It is also necessary to be able to afford this level of protection both in nominal operation and in the event of a partial or complete malfunctioning of the electric traction system.
The following documents are known from the prior art.
Document US20090033264A1 discloses a standard device for limiting and regulating the speed of a vehicle.
Document WO200735146A1 discloses a device providing speed control of a component of the drivetrain of a motorized vehicle.
Document WO201023998A1 describes a device for regulating and limiting the speed of a motor vehicle.
There therefore remains a need for a control system and method which are able to prevent a risk of electric traction machine overspeed during operation.